1. Field of Invention
The invention relates to tooling and more specifically to a tool for installing insert rings and aligning pipes to be joined by welding.
2. Summary of the Prior Art
Joining of pipes using multi-path welding techniques presents many complex problems. The goal is to produce a weld having mechanical properties, such as yield strength, at least equal to the remainder of the pipe. This goal is not achievable using current techniques.
Problems common to all current pipe welding processes include stresses induced by welding, incomplete fusion of the welding material with the pipe and uneven interior surfaces. The use of insert rings is one technique currently used to improve the characteristics of welds.
Typically, the two ends of the pipe to be joined together are beveled and an insert ring positioned between the two ends prior to the first welding pass. Tack welding at a plurality of radially spaced locations is used to hold the insert ring in position. During the first welding pass, the insert ring is melted and fuses with the two ends of the pipe to form a relatively smooth interior surface. Successfully joining two ends of the pipe using this technique requires that the insert ring and the two ends of the pipe be properly prepared and aligned and the insert ring tack welded, as described above, prior to the first welding pass.
Considerable effort has been devoted to solving the above discussed problems. Typical prior art welding processes are summarized in the following patents which were noted during a prior art search related to the present invention.
U.S. Pat. No. 4,625,414 discloses a gage for holding insert rings in position while they are tack-welded in place. Automatic methods for welding the ends of two pipes together are illustrated in U.S. Pat. No. 4,213,555. Alignment of the ends of a pipe using an alignment ring inserted into the interior of the pipe are illustrated in U.S. Pat. No. 3,960,311.
U.S. Pat. No. 3,910,481 discloses backup tools adapted for insertion into tubular pipes to be drawn together by welding. Clamping techniques for holding first and second sections of pipe in a fixed position as they are welded together in end-to-end relationship is illustrated in U.S. Pat. No. 3,901,497.
Techniques for controlling the shape of cylindrical structures during welding are illustrated in U.S. Pat. No. 3,149,597. Centering rings for aligning a backup ring is illustrated in U.S. Pat. No. 3,101,532. Techniques useful in welding pipes are further illustrated by U.S. Pat. No. 2,449,371, U.S. Pat. No. 3,002,191, and U.S. Pat. No. 2,584,072.